Along with the advance in the integration of semiconductor elements, the patterns formed by lithography systems are making progress in microfabrication. In the progress, however, it is considered to be difficult to form contact holes arranged at smaller pitches. In order to form the contact holes at smaller pitches by conventional technologies, there is used a technique in which a square mask pattern is formed by biasing a mask data or design data and the mask is transferred onto a wafer. For instance, in order to form contact holes arranged at pitches of 240 nm and each having a diameter of 120 nm by an ArF aligner under the illumination conditions of numeral aperture (NA)=0.7 and σ=0.7, the patterns on the mask come to be a square pattern each having a diameter of 160 nm, which requires a bias of approximately 40 nm to be stably formed.
This technique allows the contact holes to be formed, however, it increases the light intensity at a light shielding part to sometimes cause a failure such as a reduction in resist film thickness or disconnection.
Further, when fabricating a mask, a mask is normally biased in consideration of the influence of optical proximity effect (OPC: Optical Proximity Correction). The correction value for the bias should consider the influence of the optical proximity effect, the influence of etching proximity effect, the influence of pattern shapes in the mask manufacturing processes, and the like. At this time, a difference caused in the mask manufacturing processes leads to a change in the optical proximity correction value. That is, every change in the mask manufacturing processes requires a recalculation of an optimal value for the optical proximity correction, complicating the optical proximity correction and requiring a huge range of steps in addition thereto.
Therefore, an object of the present invention is to provide a photomask capable of forming desired micro actual patterns easily and accurately by forming a resist pattern without causing a failure in manufacturing a device such as a reduction in resist film thickness, a disconnection between actual patterns such as contact holes, or so forth even if the patterns are arranged at small pitches, and by simplifying an optical proximity correction by way of eliminating the factor of the mask manufacturing processes from the optical proximity correction; and a manufacturing method of the same; and a pattern forming method.